1. Field of the Invention
This invention relates to an aqueous coating composition which contains an amino group-containing organopolysiloxane and a surface-active agent and has superior uniform-coating properties and storage stability.
2. Description of the Prior Art
In recent years, environmental regulations have become severe in relation to volatile organic compounds and to how toxicity and so forth be lessened. Also, from the viewpoint of saving of natural resources, coating compositions are being changed over from a system making use of organic compounds as solvents to a system making use of water. Amino group-containing organopolysiloxanes can be made water-soluble even in a high concentration because of the polar effect of amino groups, and are used as primers for metal or metal oxide surfaces, additives of acrylic latex sealants, coupling agents for particle surfaces of inorganic fillers such as silica, and binding agents of aqueous coating materials. They are also used as aqueous materials for the formation of organic glass films in semiconductor device fabrication processes.
However, aqueous solutions of amino group-containing organopolysiloxanes have a high surface tension, and hence there has been a problem that the phenomenon of cissing may occur when coated on the surfaces of metals, metal oxides or organic coatings, in particular, on flat-plate surfaces, so that any uniform coatings can not be formed.
To solve this problem, a method is known in which a surface-active agent is added. There, however, has been a problem that the surface-active agent may decompose on lapse of time because of a strong alkalinity due to the amino groups, and its effect does not last.
An object of the present invention is to provide an aqueous coating composition which contains an amino group-containing organopolysiloxane and a surface-active agent and has superior uniform-coating properties and storage stability.
To solve the above problems, the present inventors made extensive studies. As the result, they have discovered that an aqueous coating composition as described below can solve the problems, and have accomplished the present invention.
That is, the present invention provides an aqueous coating composition comprising (A) an amino group-containing organopolysiloxane, (B) water and (C) at least one of i) a surface-active agent represented by the following general formula (I): 
wherein R1 to R4 are each independently an alkyl group having 1 to 8 carbon atoms, R5 and R6 are each independently an alkylene group having 1 to 6 carbon atoms, R7 and R8 are each independently a member selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms and an acyl group having 2 to 6 carbon atoms, and m and n are each an integer of 0 to 40, provided that m and n are not 0 at the same time and that the value of m+n is a number of 1 to 40 on the average; and ii) a nonionic surface-active agent containing a perfluoroalkyl group and an alkylene oxide group;
the component (C) being present in a content of from 0.01% by weight to 5% by weight based on the total weight of the components (A), (B) and (C), and an alcohol being present in the composition in an amount not more than 10% by weight of the total weight of the composition.